Dye mordants capable of converting to non-mordanting species in the presence of alkali are known. Such mordants have been disclosed for use in photographic elements to retain in a given layer of the element a light-filtering or anti-halation dye, such retention being of particular benefit in the manufacturing and storage of the element. During processing of the element in an alkaline processing bath, the mordant material undergoes a chemical change effectively destroying the mordanting capacity of the material and, thus, facilitating release of the dye from its layer and desired removal or bleaching of the dye from the photographic element.
Thus, U.S. Pat. No. 3,575,993 relates to certain mordant materials comprising a quaternary nitrogen moiety attached to a bulky residue and disclosed to be useful for retention of organic acid light-filtering and anti-halation dyes in appropriate layers of a photographic element. The mordant materials are further disclosed to be capable of releasing the mordanted dye during processing of the element in an alkaline processing bath, thus, facilitating desired removal of the dye from the element. Release of the dye is disclosed to be accomplished by alkali-induced destruction of the mordanting capacity of the mordant material, either by decomposition of the mordant to separate the quaternary nitrogen fragment from the bulky residue or by a rearrangement reaction which produces a zwitterion with resultant internal charge compensation and loss of mordanting capacity. In addition to allowing release of light-filtering and anti-halation dyes from the mordanted layer, the destruction of mordanting capacity is also disclosed to minimize retention in the element of sodium thiosulfate fixer used in the processing of the element. Additional U.S. patents relating to the mordant materials disclosed in U.S. Pat. No. 3,575,993 and to photographic elements comprising such mordant materials are U.S. Pat. Nos. 3,444,138 and 3,455,693.
U.S. Pat. No. 3,425,833 relates to certain quaternary nitrogen mordant materials comprising a phenolic residue. These mordant materials are also disclosed to be useful for retention of organic acid light-filtering and anti-halation dyes in photographic layers and to be capable of releasing the dye in the presence of an alkaline processing bath. The mechanism of dye release is disclosed to involve conversion of the mordant material to a zwitterionic species with resultant loss of mordanting capacity.
U.S. Pat. No. 3,425,834 discloses various mordant materials also intended for utilization in the retention and subsequent release of light-filter and anti-halation dyes in photographic layers. The subject mordants are disclosed to comprise alkali-cleavable alkylamino groups or nitrogen heterocyclic nuclei attached to a bulky residue. As disclosed therein, the processing of a photographic element containing a layer of the mordant material in an alkaline processing bath functions to destroy the mordanting capacity of the material by means of alkali-induced cleavage of the material with a resultant splitting-off of the mordanting nitrogen moiety from the bulky residue. As a result, removal of the mordanted dye from the system is facilitated and retention of thiosulfate ion from the fixing bath used in processing is disclosed to be minimized.